Self-bending airborne ultrasound beam using a binary lens based on the Airy function

Abstract

Self-bending of a beam of sound was previously achieved by an acoustic metasurface that modified the amplitude and phase modulations. However, fabricating a fine-structured device for ultrasound is difficult because it has a short wavelength. In this paper, we propose a simple binary acoustic lens for a self-bending ultrasound beam in air at 40 kHz. The lens has transparent and opaque areas and was designed using the Airy function. The beam bending was evaluated by simulations and experiments. The simulations showed that the proposed lens achieved beam self-bending, although the concentration of energy in the main beam was inferior to that for phase-coded modulation. The experiments demonstrated that self-bending is feasible using a binary lens made of a polypropylene sheet, and the measured sound fields agreed well with the simulations. These results suggest that a self-bending beam of ultrasound is possible with a lens having a simple binary structure.

Enhancement of convergence efficiency for airborne ultrasonic self-bending beam with phase-modulating reflector

“…Phase-coded modulation Some studies have shown that it is possible to generate a selfbending beam by controlling the spatial phase distribution of sound waves with a binary system based on the Airy function. 2,[10][11][12]23) Here, we call the method that controls the spatial phase distribution with binary values, π rad or 0 rad, "phase-coded modulation. "…”

“…In our previous work, we simulated the self-bending beam with ultrasound in air assuming that the emitter has the spatial phase distribution that we applied to the present reflector design. 23) The simulation was performed with the finite element method in two-dimensional space (x, z). The simulation model was a rectangle measuring 0.6 m × 1.0 m. The Sommerfeld acoustic radiation condition was set on the outer boundary.…”

“…We have previously produced a self-bending beam for airborne ultrasound by installing amplitude modulation with a lens that is made of plastic plates with a binary configuration, namely transparent and opaque, based on the Airy function. 23) However, the proposed binary lens method has shown a lack of sound pressure convergence into the main pressure lobe, and, therefore, the binary lens has produced numerous spreading grating lobes. 23) This is a critical issue in light of the prospective applications using the airborne ultrasonic self-bending beam.…”

“…23) However, the proposed binary lens method has shown a lack of sound pressure convergence into the main pressure lobe, and, therefore, the binary lens has produced numerous spreading grating lobes. 23) This is a critical issue in light of the prospective applications using the airborne ultrasonic self-bending beam. Applications using airborne ultrasound include, for example, haptics, 24) generation of audible sound.…”

Phonon Focusing Effect in an Atomic Level Triangular Structure

“…DOI: 10.1088/0256-307X/40/9/096301 Manipulating wave transport by artificial materials is a hot topic in recent years. [1][2][3] The rapid development of metamaterials has also brought new ideas for designs of acoustic or optical devices with special functionalities, such as beam focusing, [4][5][6][7] asymmetric transmission, [8][9][10][11] self-bending beams, [12][13][14] cloak, [15][16][17] and perfect absorption. [18][19][20] In addition to modulations of light and sound, there have been growing efforts in applying phononic crystals to control of thermal waves as well, [21][22][23][24] namely, the heat.…”